The Transportation Authority of Marin’s Board of Commissioners will send letters to state and Bay Area transportation agencies requesting they consider a shorter trial run for a proposed bike-pedestrian lane on the Richmond-San Rafael Bridge.

A third westbound lane set to open in April or May was proposed to be a four-year pilot project in which only pedestrians and cyclists could access the lane.

Along with the requests, the Transportation Authority Marin board approved allocating $148,000 for a study on the potential traffic impacts that a third lane of vehicle traffic could have in Marin County. The board also requested that Caltrans conduct a study to determine whether the bridge could structurally support opening up the lane to vehicle commuters.

Damon Connolly, a Marin County supervisor and transportation authority board member, said the board hopes to have both studies completed within six months.

“At the end of the day what we’re saying is four years is too long,” Connolly said Friday. “Six months is a good time period where at least by then we have some data on usage of the lane and we’re also further down the road on these additional two studies.”

Connolly, who also serves on the Metropolitan Transportation Commission, said the six-month review doesn’t necessarily mean the pilot project would be cut to six months, but would be a point at which such a consideration could be made.

Fellow board members Eric Lucan, who is also Novato’s mayor, and Fairfax Councilman John Reed voted against the proposal. Lucan said he opposed it because of the letter requesting a six-month trial period, though he said he supports the requested traffic impact and structural studies.

Lucan argues the information from these studies, such as whether the bridge can structurally support the increased traffic and a proposed moveable barrier, should be obtained before considering any requests to shorten the bike lane pilot project.

“I thought it was putting the cart before the horse a little bit,” Lucan said about the board’s vote.

Cyclist groups like Bike East Bay have come out in opposition to the transportation authority’s request, while Marin County Bicycle Coalition executive director Jim Elias has called for the authority to give careful consideration to several issues including impacts to commuters, the environment and cyclist commuters.

“I wish this project realistically promised to do all of those things, but I do have some doubts,” Elias said. ‘We’re asking you to not view this as a moment in time to choose between bikes or cars, but to honor or remain focused on the bigger prize, which is to design opportunities for travelers to cross the bridge more efficiently, more economically and with less impact to the environment than with single-occupancy cars.”

The board also expressed interest in looking at “multi-modal” use of the lane, such as programs to incentivize carpooling and improve transit.

“We would love to hear from the public on any input they have and we look forward to continuing collaboration with stakeholders as we continue to look at the possibilities for this third lane,” Connolly said.